Induction electric furnace



P 22, 1931- E. F.INORTHRUP 1,824,618

INDUCTION ELECTRIC FURNACE Filed Juiy 9. 1929 2 Sheets-Sheet 1 4 T l ni V i 'l 204 l wmpbgv Sept 22, 1931. 5. r--. NORTHRUP 1,324,518

INDUCTION ELECTRIC FURNACE Filed July 9. 1929 2 Sheet-Sheet 2 Patented Sept. 1931 UNITED STATES PATENT OFFICE EDWIN FITCH noamur. OI PRINCETON, NEW JERSEY, ASSIGNOB '10 AJAX ELECTRO- THERIIC CORPORATION, AJAX PAB K, NEW JERSEY, A CORPORATION O! m msn! v Application fled July 0,

My invention relates to induction electric furnaces of the coreless type.

A purpose of my invention is to provide for water cooling of a focus inductor type of furnaee.

A further purpose isto make the fluid resistance of water flow in cooling low in focus inductor furnaces.

A further purpose is to improve the coupling between a focus inductor coil and its primary coil in a coreless furnace.

A further purpose is to reduce the injury in case of leakage flow of molten metal to the immediate parts with which contact of 5 the metal takes place.

A further purpose is to increase the efficiency of an inductor furnace.

A further purpose is to simplify the mechanic'al construction of a furnace. A further purpose is to water cool the individual inner and outer turn or turns of each section of a focus inductor in parallel and to water cool in parallel the several sections greatly reducing the resistance to water flow.

Further urposes will appear in the specification an in the claims.

This invention is applied to the neral type of inductor furnace shown in my atent No. 1,378,187 of May 17, 1921. Though applicable to the forms of focus inductor connection shown in Figures 12-21 and 28, the princi leis so well shown in furnaces of the type s own in Figures 24 and 25 that I have preferred to illustrate figures of this general type only, intending, however, to make my claims broad enough to cover application of the invention to the other type also.

The invention has, therefore, been shown in connection with the concentric form of focus inductor onl the illustrations, to essentially the same orm, differing only in that both meltin and heating furnaces are illustrated and t e melting furnace is shown with and without magnetic core to improve the cou ling of the primary and focus inductor.

li igure 1 is a to plan view of a focus inductor furnace embo ying my invention with the water supply pipes in section.

Figure 2 1s a vertical section of such a furnace taken upon lines 22 of Figure .1.

ma. Serial No. 876,821.

Figure 3 is a vertical section corresponding to Figure 2 but omitting the magnetic coupling between the'primary and the focus inductor.

Figure 4 is a perspective view of one of the 'Fi res 1,2 and 3.

re 1. igure 6 is a central longitudinal section through an inductor which is applied to heatin travelling stock.

n the drawings similar numerals indicate like parts.

In Figures 1-5 I show means for holdin and heat insulating a molten pool which is intended to be diagrammatic as it may be greatly varied, but which as shown includes a crucible 9, refractory 10 and a casing 11 about the refractory holding it in lace and acting as an insulator between it an the inner turns of the focus inductor 12.

The character of holding means for the melt will depend upon the needs of the furnace and the refractory will differ according to whether it be intended for low-meltin point or high-melting point metals and whether or not it be intended to sinter with contact from the leakage molten metal. vFor low-melting point metals asbestos wool could be used but for higher temperatures or where sintering is desired it is desirable to use finely divided refractories having a sand or chrome ore base. Micanite is quite suitable for the retaining and insulating shell 11.

The arts as so far described are supported upon BHJRSG 13. It may form any convenient heat insulating support for which alberene stone is well suite The focus inductor 12 surrounds the furnace with its inner turns 14 as close to the material as is safe in order to get as close coupling with the charge as possible. The outer turns 15 are spaced from the inner turns far enough to get away from the heat of the furnace, thus s acing the primary inductor 16 to a point w ere the temperature is relatively cooler and where it can be insulated to the best advantage. It induces current in the outer and inner turns in series as in the focusing coils of the 'focus inductor, seen inigure 5 is a section taken upon line 5-5 of the'division between the nections between the pa case of the focus inductor furnace described in my patent previously referred to.

The focus inductor turns are shown as com prising individual inductor turns (Fi ure 4) 1n arallel one with another, electrics. y and by raulically. The inductor is of hollow fiat tubing and is shown as flat-wound, as distinguished from edge-wound.

'nigples 19 and 20, the nipples for the several 2c in uctor sections being connected in parallel from supply pipes 21 and 22 which may he flexible or rigid as is found most convenient.

I The rimary inductor winding 16 is supplied with alternating current-from mains 23 and 24, which current supply is shown as cor- I 'rectedfor power factor by capacity 25 which 1'9. thrown across the mains. This primary pouring spout 26 to the mold t coil can be water-cooled, if desired, inany of the usual ways.

In order to permit close approach of the e outer focus inductor turn 15 is shown as flattened at 27.

The current is su plied to the primary coil at a relatively. hig voltage. Because of its sition at considerable distance from theurnace pool it can be insulated well without complication from the higher temperatures present nearer to the pool and can be con led to the outer focus inductor turns as close y as the electrical insulation will permit. The focus inductor coils carry current at so low a voltage that but little attention need be paid to their insulation. The are there fore well suited from an electrica standpoint to lie very close to the molten'metal.

In operation the current in the main, inductor induces opposite current in the adjoinin (outer) turns of the focus inductor, with t e result that the current in theinner focus inductor turns flows in the same direction as that of the primer inductor. There is substantially no externa or stray field outside of the primary. v

.The water flow takes place through the different focus inductor coils in arallel and within the individual coils also ows in parallel through the inner and outer turns greatly reducing the resistance of the hand how.

and makin it possible to secure the requisite cooling wit a minimum of water pressure.

The only difference between the form shown in rigures l and 2 and that in Figure 3 lies in the fact that the coupling between the primary inductor coil and the focusinductor coils within it in Figures 1 and 2 is imlcan come upon the cruel charge can be It will be 0 vious also that the construesesame proved by the use of a return magnetic circuit comprising iron or steel legs 28 and 29 res ectively inside and outside the primary in uctor and outer turns of the focus inductor. The legs are magneticall connected dent from a single example shown in Figure 6 where the common axis of the primary inductor 16' and focus inductor 12' is l'lOllZOIltal and where both of the coils surround travelling stock 32 here shown as a section of T heillustration may represent one coil only of a series of coils or may constitute the entire heating equipment according to the needs met. The travelling stock is supgorted upon concave rollers 33, and may be riven by them.

.In connection with or separate from water cooling, of which an exam leis seen in F1gures 1-5, I may use air c cling lag delivery of an air blast between the focus in uctor and the travellin stock through any conventional nozzle 34. are no melting takes place the inner coils of the focus inductor can be located quite close to the travelling stock,

greatly improving the coupling. Neither.

heat insulation nor ealgpgrical insulation is necessary if slight sp g be efiected hythe rollers.

In all forms the coils as arran ed are substantially' without external 'fiel and" can, therefore be supported'in a metallic case,

if desire Even with the highest primary the voltage whic is or charge is not 50'v'olts and the crucible or unded at one point.

voltages now customary greater than tion is sim lo and odors no mechanical difficulties. case of 'iniuri to any focus inductor part the injury to the part afiected and requires a minimum amount of repairs or replacement. a

It will be obvious that the a through improved coupling is 11kt fie loss through additional Mal eoilresimnce and that high efiiciency ,camtherefore, be attained. l

In view of my invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art to obtain all or'part of the benefits of my invention without copying the structure shown, and I, therefore, claim all such in so far as they fall the reasonable spirit and scope of m invention.

Having thus ascribed iny invention, what 1. A focus inductor comprising. a primary coil and inner and outer hollow focus inductor coils in series, one forming a sec ondary to the primary and the other about the charge, and fluid connections passing the fluid through the two focus inductor coils in parallel.

2. A primary inductor and a focus inductor within it comprising a plurality of sections electrically in parallel, each having outer turns secondary to the primary inductor and inner turns forming-primaries to the charge and water-cooling in parallel through the outer and inner turns of each section.

. 3. A primary inductor and a focus, inductor within 1t, comprising a plurality of sections in parallel, each having outer turns secondary to the primary inductor and inner turns forming rimaries to the char e, the several focus inductors being electrica y and hydraulically in parallel.

4. A hollow focus inductor section having inner and outer turns and water connections placing the turns in arallel.

5. A hollow focus inductor section having inner and outer turns, water connections passing the water throu h the coil in arallel paths and a ma etic return path etween the inductor section turns.

6. A flattened and flat-wound hollow focus inductor section having inner and outer turns and water connections placing the turns in parallel.

7. A primary coil, a focus inductor coil 7 within the primary having inner and outer coils connected in series and a magnetic return path between the focus inductor coils.

8. -A rimary coil 9. focus inductor coil within the primary having inner and outer coils connected in series, and a magnetic return 'ath between the focus inductor coils and a so outside the primary inductor.

. 9. In an induction furnace, a focus inductor secondary winding havin inner and outer concentric coils electrically in series, a pri mary inductor outside of the outer focus in ductor coil and a magnetic return circuit located inside and also outside the primary inductor.

10. In an inductor furnace, a focus inductor secondary winding thereabout having concentric inner and outer coils in series, a

rimary inductor outside of the outer focus inductor coil, and a magnetic return circuit located inside and outside the primar inductor and within the outer coil of the ocus inductor.

' 11. In a coil system, an outer primary coil, 8. source of alternating current therefor, a pair of secondary coils coaxial with the outer coil and with each other within the outer coil, connected in series and a magnetic return circuit for the system;

12. In a coil system, an outer coil, a source of alternating current therefor, a pair of coils coaxial with the -outer coil and with each other,within the outer coil, connected in series, and a magnetic return circuit threading between the pair of coils and extending outside of the outer coils.

I 13. In a coil system, an outer coil, a source of alternating current therefor, a pair of coils coaxial with the outer coil and with each other connected in series and a magnetic return circuit threadingbetween the coils of the pair, extending outside of the outer coil and also across one end of the coils to a distance from the coil axis shorter than the radius of the innermost coil.

14. In a heating system, an outer coil, a horizontal axis focus inductor therein comprising inner and outer turns connected in series and a support for an article to be heated adapting it to move horizontally within the inner turn of the focus inductor.

15. In a heating system, an outer coil having a horizontal axis, a focus inductor therein comprisin sectionsin parallel, each having inner an outer turns connected in series and a support for an article to be heated within the inner coil. i

16. In a heating system, an outer coil having a horizontal axis, a focus inductor therein comprising inner and outer turns connected in series, water cooling means for cooling the focus inductor and a support for an article to be heated within the inner coil.

. EDWIN F. NORTHRUP. 

